BEHAVIOR TOWARD POLARIZED LIGHT. 29 



shown that they are all crystallographically identical, or at least 

 isomorphous. They probably belong to the hexagonal system and 

 are more or less markedly doubly refractive (positively). The 

 most perfect forms are obtained on repeated crystallization, while 

 as intermediary forms spheroids and globulits are commonly encoun- 

 tered. If the crystallization is repeated too often, the crystalline 

 appearance may be lost and the body again becomes amorphous. 



Diffusion. Like the colloids of the inorganic world, so also are 

 the albumins incapable of diffusing through animal membranes or 

 vegetable parchment. This peculiarity Graham explained by the 

 assumption that such bodies do not occur in a state of actual solution. 

 This, however, is not the case, for it has been shown that albu- 

 minous solutions are capable of conducting the electrical current 

 and may exist both as anions and kations i. e., that they are true 

 solutions. Their inability to pass through animal membranes is 

 explained most likely by the size of the albuminous molecule. This 

 property is very important from the standpoint of chemical tech- 

 nique, as it renders it possible to separate the albumins from a 

 large number of other bodies which may simultaneously be present 

 in solution. Colloids in the soluble state are termed sols ; in the 

 solid state, gels. When dissolved in water they are known as hydrosols. 



Behavior toward Polarized Light. All true albumins are 

 Isevorotatory, the degree of rotation being different in different 

 members of the group. This fact has been utilized in the identi- 

 fication of the individual albumins, but it is to be noted that unless 

 the examinations can be made with neutral aqueous solutions the 

 resulting data will not be constant. Biilow has definitely proved 

 that the same albuminous solution will show a varying degree of 

 rotation with a varying reaction. Some of the results which have 

 been obtained are given in the following table : 



Animal albumins. Vegetable albumins (Osborne). 



Serum-albumin ()D . . . . 56 Edestin (hempseed) 



Serum-globulin 59-75 (a)D 41.3 



Fribrinogen 43 Globulins (various 



Egg-albumin _33o_ 38 o f oims ) 38.78-45.21 



Lactalbumin 36-37 Excelsin (Brazilnut) . 42.94 



Casein (in MgSO 4 solution) . 80 Amandin (almonds) . . 56.44 



Syntonin (from myosin) . . 72 Corylin (filbert) . . . 43.09 



Alkaline albuminate .... 62.2 Zein (maize) 28.00 



Various albumoses 70-80 Gliadin (wheat) . . . 92.28 



Phaseolin (kidney bean) 41.46 



While Isevorotation is constant in the true albumins, dextrorota- 

 tion probably occurs in all nucleoproteids. This has been estab- 

 lished directly in the case of the nucleoproteids of the pancreas, 

 the thymus and the adrenal glands (Gamgee, Jones), and Osborne 

 has shown that this property is very likely wholly referable to 

 the nucleinic acid component. The degree of dextrorotation in the 

 substances which thus far have been examined varied between 

 -f 37.5 fnncleohiston from thymus) and 97.9 (Hammarsten's 

 /9-nucleoproteid of the pancreas). 



